Figures

Figure 1a

Schematic picture of the structure of sample A.

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Figure 1b

Schematic picture of the structure of sample B.

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Figure 2

Measured (black thin line) and simulated (thick red line) 0002 profiles of sample A.

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Figure 3

Asymmetric 10-15 reciprocal space mapping of sample A. The vertical line marks the direction of fully strained growth of the MQW structure.

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Figure 4

Photoluminescence spectra of sample A at 2 K and low cw excitation intensity.

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Figure 5a

Temperature dependence of the main emission peak Q1 of sample A at excitation power P = 0.006 mW. Experimental data are fitted with the expression E = E(0) - T²/(T + ) - ²/kT.

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Figure 5b

Same as Figure 5a but at excitation power P = 0.6 mW.

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Figure 6

Low-temperature PL spectra of sample A at different excitation powers. The spectra are shifted for clarity. The dashed lines are guide to the eyes.

Figure 7

Energy position of the Q1 and Q2 emission peaks as a function of the excitation power. The lines are guide to the eyes.

Figure 8a

PL spectra of sample A at different temperatures between 5 K and 55 K.

Figure 8b

PL spectra of sample A at temperatures above 60 K.

Figure 9

Photoluminescence excitation spectra of sample A.

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Figure 10

Sketch of the potential variation across the MQW region for sample A.

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Figure 11

Low temperature PL spectra of the sample A at different excitation energies below the barrier bandgap. The arrows indicate the excitation energies.

Figure 12

Low temperature PL transients of sample A measured for selected photon energies.

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Figure 13

Time-resolved spectra of sample A measured at different temperatures: 2 K (a), 70 K (b) and 250 K (c). The time interval between each spectrum is 1.9 ns.

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Figure 14

Temperature dependence of the photoluminescence decay time of Q1 and Q2 transitions.

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Figure 15

PL spectra of sample B at T = 2K.

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Figure 16

PL spectra of sample B at different excitation intensities. The spectra are normalized and shifted for clarity.

Figure 17a

Temperature dependent PL spectra of sample B at low excitation intensity.

Figure 17b

Temperature dependent PL spectra of sample B at high excitation intensity.

Figure 18

Sketch of the potential variation across the MQW region for sample A.

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Figure 19

Photoluminescence transients for Q1 and Q2 transitions of sample B at T = 2 K.

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Figure 20

Time-resolved PL spectra for sample B with different external bias: (a) -4V and (b) +4V. The top spectrum is a time-integrated spectrum shown for comparison. The delay time between successive spectra is 3.5 ns.

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Figure 21

Photoluminescence (PL) and electroluminescence (EL) of sample B at different applied biases and T = 2 K. There is a series resistance in the electrical wires down to the sample in the cryostat, so the real bias over the sample is smaller by a factor two. The EL spectra are obtained without optical excitation with DC bias.

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